Nrf2-dependent gene expression is affected by the proatherogenic apoE4 genotype-studies in targeted gene replacement mice

The Gut-Brain Axis in Alzheimer's and Parkinson's Diseases: The Catalytic Role of Mitochondria

Accumulating evidence suggests that gut inflammation is implicated in neuroinflammation in Alzheimer's and Parkinson's diseases. Despite the numerous connections it remains unclear how the gut and the brain communicate and whether gut dysbiosis is the cause or consequence of these pathologies. Importantly, several reports highlight the importance of mitochondria in the gut-brain axis, as well as in mechanisms like gut epithelium self-renewal, differentiation, and homeostasis. Herein we comprehensively address the important role of mitochondria as a cellular hub in infection and inflammation and as a link between inflammation and neurodegeneration in the gut-brain axis. The role of mitochondria in gut homeostasis and as well the crosstalk between mitochondria and gut microbiota is discussed. Significantly, we also review studies highlighting how gut microbiota can ultimately affect the central nervous system. Overall, this review summarizes novel findings regarding this cross-talk where the mitochondria has a main role in the pathophysiology of both Alzheimer's and Parkinson's disease strengthen by cellular, animal and clinical studies.

APOE-Genotype and Insulin Modulate Estimated Effect of Dietary Macronutrients on Cognitive Performance: Panel Analyses in Nondiabetic Older Adults at Risk of Dementia

BACKGROUND

The apolipoprotein E gene (APOE ε-2/3/4, combined as 6 different genotypes: ε-22/23/24/33/34/44) and insulin status modulate dementia risk and play a role in the metabolism of macronutrients.

OBJECTIVES

We aimed to examine APOE-genotype and fasting insulin as effect modifiers of the slopes between dietary macronutrients and cognitive performance among older adults at risk of dementia.

METHODS

Panel analyses-with diet and cognition measured at baseline and follow-up at years 1 and 2-were performed in a sub-sample from the FINGER (Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability) trial (n = 676, 60-77 y, 46% females, all nondiabetics). The associations between macronutrients (3-d food records, z-scores) and global cognition (modified Neuropsychological Test Battery, z-score) were analyzed in mixed regression models adjusted for confounders selected a priori. After a gradient was implied by the point estimates in categorical APOE analyses, we investigated a continuous APOE variable [APOE-gradient, coded -1 (for ε-23), -0.5 (ε-24), 0 (ε-33), 1 (ε-34), 2 (ε-44)] as an effect-modifier.

RESULTS

At increasing levels of the APOE-gradient, a relatively more favorable slope between diet and cognition was observed for a lower carbohydrate/fat ratio [β = -0.040, 95% confidence interval (CI): -0.074, -0.006; P = 0.020 for interaction diet × APOE-gradient), and higher protein (β = 0.075, 95% CI: 0.042, 0.109; P = 9.4 × 10-6). Insulin concentration (log-linear) modulated the association between the carbohydrate/fat ratio and cognition by a quadratic interaction (β = -0.016, P = 0.039). Coherent findings for exploratory predictors (fiber, fat subtypes, composite score, metabolic biomarkers) were compatible with published hypotheses of differential dietary adaptation by APOE, with cognition among ε-33 being relatively independent of dietary parameters-implying "metabolic flexibility." Antagonistic slopes to cognition for ε-23 (positive) compared with ε-34 and ε-44 (negative) were found for a Higher-carbohydrates-fiber-Lower-fat-protein composite score, even as within-subjects effects.

CONCLUSIONS

APOE-based precision nutrition appears conceptually promising, but replications in wider samples are warranted, as well as support from trials. Both relative hyper- and hypoinsulinemia might modulate the effect of diet on cognition.

Dietary Responses of Dementia-Related Genes Encoding Metabolic Enzymes

The age-related loss of the cognitive function is a growing concern for global populations. Many factors that determine cognitive resilience or dementia also have metabolic functions. However, this duality is not universally appreciated when the action of that factor occurs in tissues external to the brain. Thus, we examined a set of genes involved in dementia, i.e., those related to vascular dementia, Alzheimer's disease, Parkinson's disease, and the human metabolism for activity in 12 metabolically active tissues. Mining the Genotype-Tissue Expression (GTEx) data showed that most of these metabolism-dementia (MD) genes (62 of 93, 67%) exhibit a higher median expression in any of the metabolically active tissues than in the brain. After identifying that several MD genes served as blood-based biomarkers of longevity in other studies, we examined the impact of the intake of food, nutrients, and other dietary factors on the expression of MD genes in whole blood in the Framingham Offspring Study (n = 2134). We observed positive correlations between flavonoids and HMOX1, taurine and UQCRC1, broccoli and SLC10A2, and myricetin and SLC9A8 (p < 2.09 × 10-4). In contrast, dairy protein, palmitic acid, and pie were negatively correlated, respectively, with the expression of IGF1R, CSF1R, and SLC9A8, among others (p < 2.92 × 10-4). The results of this investigation underscore the potential contributions of metabolic enzyme activity in non-brain tissues to the risk of dementia. Specific epidemiological or intervention studies could be designed using specific foods and nutrients or even dietary patterns focused on these foods and nutrients that influence the expression of some MD genes to verify the findings presented here.

Sex and APOE Genotype Alter the Basal and Induced Inflammatory States of Primary Microglia from APOE Targeted Replacement Mice

The sex and APOE4 genotype are significant risk factors for Alzheimer’s disease (AD); however, the mechanism(s) responsible for this interaction are still a matter of debate. Here, we assess the responses of mixed-sex and sex-specific APOE3 and APOE4 primary microglia (PMG) to lipopolysaccharide and interferon-gamma. In our investigation, inflammatory cytokine profiles were assessed by qPCR and multiplex ELISA assays. Mixed-sex APOE4 PMG exhibited higher basal mRNA expression and secreted levels of TNFa and IL1b. In sex-specific cultures, basal expression and secreted levels of IL1b, TNFa, IL6, and NOS2 were 2−3 fold higher in APOE4 female PMG compared to APOE4 males, with both higher than APOE3 cells. Following an inflammatory stimulus, the expression of pro-inflammatory cytokines and the secreted cytokine level were upregulated in the order E4 female > E4 male > E3 female > E3 male in sex-specific cultures. These data indicate that the APOE4 genotype and female sex together contribute to a greater inflammatory response in PMG isolated from targeted replacement humanized APOE mice. These data are consistent with clinical data and indicate that sex-specific PMG may provide a platform for exploring mechanisms of genotype and sex differences in AD related to neuroinflammation and neurodegeneration.

Transcriptome and Lipid Metabolomics-Based Discovery: Glycyrrhizic Acid Alleviates Tripterygium Glycoside Tablet-Induced Acute Liver Injury by Regulating the Activities of CYP and the Metabolism of Phosphoglycerides

Background: Glycyrrhizic acid (GA) has been reported to be liver protective; however, the characters and underlying mechanisms of GA against tripterygium glycoside tablet (TGT)-induced acute liver injury remain unelucidated.

Hypothesis/Purpose: We assumed that GA could relieve TGT-induced acute liver injury by regulating liver function-related genes and lipid metabolites.

Study Design: TGT-induced acute liver injury models were constructed in vivo and in vitro. Then the liver protective effect and mechanisms of GA were investigated by a combination of transcriptome, lipid metabolomics, and experimental validation.

Methods: Intraperitoneal injection of GA was given in advance for six successive days. Then, the TGT-induced acute liver injury model was constructed by a single oral administration of TGT at 270 mg/kg, except for the normal group. All animals were sacrificed 18 h later. The serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), total bilirubin (TBIL), glutathione peroxidase (GSH-PX), and superoxide dismutase (SOD) were quantified. Liver tissues were used to observe pathological changes through hematoxylin–eosin (HE) staining and selected for transcriptome and metabolome sequencing. The underlying mechanisms were analyzed and further validated both in vivo and in vitro.

Results: Pre-administration of GA markedly decreased the serum concentrations of AST, ALT, ALP, and TBIL but increased those of SOD and GSH-Px, improving the liver morphology of mice with TGT-induced acute liver injury. In addition, GA significantly increased the gene levels of Cyp2b13, Cyp2c69, Cyp3a16, Cyp3a44, Fmo3, and Nipal1. Differentially accumulated metabolites were screened and classified as phosphatidylcholine (PC) and phosphatidylethanolamine (PE). The in vitro results indicated that pre-administration of GA markedly alleviated the inhibitory effect of TGT on BRL-3A activity.

Conclusion: This study combined transcriptome, lipid metabolomics, and experimental validation to offer convincing evidence that GA alleviates TGT-induced acute liver injury partially by regulating the activities of CYP and the metabolism of PC and PE.

Biomarkers of geroprotection and cardiovascular health: An overview of omics studies and established clinical biomarkers in the context of diet

The slowdown, inhibition, or reversal of age-related decline (as a composite of disease, dysfunction, and, ultimately, death) by diet or natural compounds can be defined as dietary geroprotection. While there is no single reliable biomarker to judge the effects of dietary geroprotection, biomarker signatures based on omics (epigenetics, gene expression, microbiome composition) are promising candidates. Recently, omic biomarkers started to supplement established clinical ones such as lipid profiles and inflammatory cytokines. In this review, we focus on human data. We first summarize the current take on genetic biomarkers based on epidemiological studies. However, most of the remaining biomarkers that we describe, whether omics-based or clinical, are related to intervention studies. Then, because of their promising potential in the context of dietary geroprotection, we focus on the effects of berry-based interventions, which up to now have been mostly described employing clinical markers. We provide an aggregation and tabulation of all the recent systematic reviews and meta-analyses that we could find related to this topic. Finally, we present evidence for the importance of the "nutribiography," that is, the influence that an individual's history of diet and natural compound consumption can have on the effects of dietary geroprotection.

Apolipoprotein E Polymorphism and Oxidative Stress in Human Peripheral Blood Cells: Can Physical Activity Reactivate the Proteasome System through Epigenetic Mechanisms?

Alzheimer's disease (AD) is characterized by proteasome activity impairment, oxidative stress, and epigenetic changes, resulting in β-amyloid (Aβ) production/degradation imbalance. Apolipoprotein E (ApoE) is implicated in Aβ clearance, and particularly, the ApoE ε4 isoform predisposes to AD development. Regular physical activity is known to reduce AD progression. However, the impact of ApoE polymorphism and physical exercise on Aβ production and proteasome system activity has never been investigated in human peripheral blood cells, particularly in erythrocytes, an emerging peripheral model used to study biochemical alteration. Therefore, the influence of ApoE polymorphism on the antioxidant defences, amyloid accumulation, and proteasome activity was here evaluated in human peripheral blood cells depending on physical activity, to assess putative peripheral biomarkers for AD and candidate targets that could be modulated by lifestyle. Healthy subjects were enrolled and classified based on the ApoE polymorphism (by the restriction fragment length polymorphism technique) and physical activity level (Borg scale) and grouped into ApoE ε4/non-ε4 carriers and active/non-active subjects. The plasma antioxidant capability (AOC), the erythrocyte Aβ production/accumulation, and the nuclear factor erythroid 2-related factor 2 (Nrf2) mediated proteasome functionality were evaluated in all groups by the chromatographic and immunoenzymatic assay, respectively. Moreover, epigenetic mechanisms were investigated considering the expression of histone deacetylase 6, employing a competitive ELISA, and the modulation of two key miRNAs (miR-153-3p and miR-195-5p), through the miRNeasy Serum/Plasma Mini Kit. ApoE ε4 subjects showed a reduction in plasma AOC and an increase in the Nrf2 blocker, miR-153-3p, contributing to an enhancement of the erythrocyte concentration of Aβ. Physical exercise increased plasma AOC and reduced the amount of Aβ and its precursor, involving a reduced miR-153-3p expression and a miR-195-5p enhancement. Our data highlight the impact of the ApoE genotype on the amyloidogenic pathway and the proteasome system, suggesting the positive impact of physical exercise, also through epigenetic mechanisms.

Mouse brain transcriptome responses to inhaled nanoparticulate matter differed by sex and APOE in Nrf2-Nfkb interactions

The neurotoxicity of air pollution is undefined for sex and APOE alleles. These major risk factors of Alzheimer's disease (AD) were examined in mice given chronic exposure to nPM, a nano-sized subfraction of urban air pollution. In the cerebral cortex, female mice had two-fold more genes responding to nPM than males. Transcriptomic responses to nPM had sex-APOE interactions in AD-relevant pathways. Only APOE3 mice responded to nPM in genes related to Abeta deposition and clearance (Vav2, Vav3, S1009a). Other responding genes included axonal guidance, inflammation (AMPK, NFKB, APK/JNK signaling), and antioxidant signaling (NRF2, HIF1A). Genes downstream of NFKB and NRF2 responded in opposite directions to nPM. Nrf2 knockdown in microglia augmented NFKB responses to nPM, suggesting a critical role of NRF2 in air pollution neurotoxicity. These findings give a rationale for epidemiologic studies of air pollution to consider sex interactions with APOE alleles and other AD-risk genes.

Supplementation with nitrate only modestly affects lipid and glucose metabolism in genetic and dietary-induced murine models of obesity

To gain a better understanding of how nitrate may affect carbohydrate and lipid metabolism, female wild-type mice were fed a high-fat, high-fructose diet supplemented with either 0, 400, or 800 mg nitrate/kg diet for 28 days. Additionally, obese female db/db mice were fed a 5% fat diet supplemented with the same levels and source of nitrate. Nitrate decreased the sodium-dependent uptake of glucose by ileal mucosa in wild-type mice. Moreover, nitrate significantly decreased triglyceride content and mRNA expression levels of Pparγ in liver and Glut4 in skeletal muscle. Oral glucose tolerance as well as plasma cholesterol, triglyceride, insulin, leptin, glucose and the activity of ALT did not significantly differ between experimental groups but was higher in db/db mice than in wild-type mice. Nitrate changed liver fatty acid composition and mRNA levels of Fads only slightly. Further hepatic genes encoding proteins involved in lipid and carbohydrate metabolism were not significantly different between the three groups. Biomarkers of inflammation and autophagy in the liver were not affected by the different dietary treatments. Overall, the present data suggest that short-term dietary supplementation with inorganic nitrate has only modest effects on carbohydrate and lipid metabolism in genetic and dietary-induced mouse models of obesity.

Cyclic O3 exposure synergizes with aging leading to memory impairment in male APOE ε3, but not APOE ε4, targeted replacement mice

The etiology of late-onset Alzheimer's disease is unknown. Recent epidemiological studies suggest that exposure to high levels of ozone (O₃) may be a risk factor for late-onset Alzheimer's disease. Nonetheless, whether and how O₃ exposure contributes to AD development remains to be determined. In this study, we tested the hypothesis that O₃ exposure synergizes with the genetic risk factor APOE ε4 and aging leading to AD, using male apolipoprotein E (apoE)4 and apoE3 targeted replacement mice as men have increased risk exposure to high levels of O₃ via working environments and few studies have addressed APOE ε4 effects on males. Surprisingly, our results show that O₃ exposure impairs memory in old apoE3, but not old apoE4 or young apoE3 and apoE4, male mice. Further studies show that old apoE4 mice have increased hippocampal activities or expression of some enzymes involved in antioxidant defense, diminished protein oxidative modification, and neuroinflammation following O₃ exposure compared with old apoE3 mice. These novel findings highlight the complexity of interactions between APOE genotype, age, and environmental exposure in AD development.

The Genetic Variability of APOE in Different Human Populations and Its Implications for Longevity

Human longevity is a complex phenotype resulting from the combinations of context-dependent gene-environment interactions that require analysis as a dynamic process in a cohesive ecological and evolutionary framework. Genome-wide association (GWAS) and whole-genome sequencing (WGS) studies on centenarians pointed toward the inclusion of the apolipoprotein E (APOE) polymorphisms ε2 and ε4, as implicated in the attainment of extreme longevity, which refers to their effect in age-related Alzheimer's disease (AD) and cardiovascular disease (CVD). In this case, the available literature on APOE and its involvement in longevity is described according to an anthropological and population genetics perspective. This aims to highlight the evolutionary history of this gene, how its participation in several biological pathways relates to human longevity, and which evolutionary dynamics may have shaped the distribution of APOE haplotypes across the globe. Its potential adaptive role will be described along with implications for the study of longevity in different human groups. This review also presents an updated overview of the worldwide distribution of APOE alleles based on modern day data from public databases and ancient DNA samples retrieved from literature in the attempt to understand the spatial and temporal frame in which present-day patterns of APOE variation evolved.

Neurointegrity and neurophysiology: astrocyte, glutamate, and carbon monoxide interactions

Astrocyte contributions to brain function and prevention of neuropathologies are as extensive as that of neurons. Astroglial regulation of glutamate, a primary neurotransmitter, is through uptake, release through vesicular and non-vesicular pathways, and catabolism to intermediates. Homeostasis by astrocytes is considered to be of primary importance in determining normal central nervous system health and central nervous system physiology - glutamate is central to dynamic physiologic changes and central nervous system stability. Gasotransmitters may affect diverse glutamate interactions positively or negatively. The effect of carbon monoxide, an intrinsic central nervous system gasotransmitter, in the complex astrocyte homeostasis of glutamate may offer insights to normal brain development, protection, and its use as a neuromodulator and neurotherapeutic. In this article, we will review the effects of carbon monoxide on astrocyte homeostasis of glutamate.

Apolipoprotein E Deficiency Exacerbates Spinal Cord Injury in Mice: Inflammatory Response and Oxidative Stress Mediated by NF-κB Signaling Pathway

Spinal cord injury (SCI) is a severe neurological trauma that involves complex pathological processes. Inflammatory response and oxidative stress are prevalent during the second injury and can influence the functional recovery of SCI. Specially, Apolipoprotein E (APOE) induces neuronal repair and nerve regeneration, and the deficiency of Apoe impairs spinal cord-blood-barrier and reduces functional recovery after SCI. However, the mechanism by which Apoe mediates signaling pathways of inflammatory response and oxidative stress in SCI remains largely elusive. This study was designed to investigate the signaling pathways that regulate Apoe deficiency-dependent inflammatory response and oxidative stress in the acute stage of SCI. In the present study, Apoe^−/− mice retarded functional recovery and had a larger lesion size when compared to wild-type mice after SCI. Moreover, deficiency of Apoe induced an exaggerated inflammatory response by increasing expression of interleukin-6 (IL-6) and interleukin-1β (IL-1β), and increased oxidative stress by reducing expression of Nrf2 and HO-1. Furthermore, lack of Apoe promoted neuronal apoptosis and decreased neuronal numbers in the anterior horn of the spinal cord after SCI. Mechanistically, we found that the absence of Apoe increased inflammation and oxidative stress through activation of NF-κB after SCI. In contrast, an inhibitor of nuclear factor-κB (NF-κB; Pyrrolidine dithiocarbamate) alleviates these changes. Collectively, these results indicate that a critical role for activation of NF-κB in regulating Apoe-deficiency dependent inflammation and oxidative stress is detrimental to recovery after SCI.

Evolution of human apolipoprotein E (APOE) isoforms: Gene structure, protein function and interaction with dietary factors

Apolipoprotein E (APOE) is a member of the vertebrate protein family of exchangeable apolipoproteins that is characterized by amphipathic α-helices encoded by multiple nucleotide tandem repeats. Its equivalent in flying insects - apolipophorin-III - shares structural and functional commonalities with APOE, suggesting the possibility of an evolutionary relationship between the proteins. In contrast to all other known species, human APOE is functionally polymorphic and possesses three major allelic variants (ε4, ε3 and ε2). The present review examines the current knowledge on APOE gene structure, phylogeny and APOE protein topology as well as its human isoforms. The ε4 allele is associated with an increased age-related disease risk but is also the ancestral form. Despite increased mortality in the elderly, ε4 has not become extinct and is the second-most common allele worldwide after ε3. APOE ε4, moreover, shows a non-random geographical distribution, and similarly, the ε2 allele is not homogenously distributed among ethnic populations. This likely suggests the existence of selective forces that are driving the evolution of human APOE isoforms, which may include differential interactions with dietary factors. To that effect, micronutrients such as vitamin D and carotenoids or dietary macronutrient composition are elucidated with respect to APOE evolution.

Apolipoprotein E - A Multifunctional Protein with Implications in Various Pathologies as a Result of Its Structural Features

Apolipoprotein E (apoE), a 34 kDa glycoprotein, mediates hepatic and extrahepatic uptake of plasma lipoproteins and cholesterol efflux from lipid-laden macrophages. In humans, three structural different apoE isoforms occur, with subsequent functional changes and pathological consequences. Here, we review data supporting the involvement of apoE structural domains and isoforms in normal and altered lipid metabolism, cardiovascular and neurodegenerative diseases, as well as stress-related pathological states. Studies using truncated apoE forms provided valuable information regarding the regions and residues responsible for its properties. ApoE3 renders protection against cardiovascular diseases by maintaining lipid homeostasis, while apoE2 is associated with dysbetalipoproteinemia. ApoE4 is a recognized risk factor for Alzheimer's disease, although the exact mechanism of the disease initiation and progression is not entirely elucidated. ApoE is also implicated in infections with herpes simplex type-1, hepatitis C and human immunodeficiency viruses. Interacting with both viral and host molecules, apoE isoforms differently interfere with the viral life cycle. ApoE exerts anti-inflammatory effects, switching macrophage phenotype from the proinflammatory M1 to the anti-inflammatory M2, suppressing CD4+ and CD8+ lymphocytes, and reducing IL-2 production. The anti-oxidative properties of apoE are isoform-dependent, modulating the levels of various molecules (Nrf2 target genes, metallothioneins, paraoxonase). Mimetic peptides were designed to exploit apoE beneficial properties. The "structure correctors" which convert apoE4 into apoE3-like molecules have pharmacological potential. Despite no successful strategy is yet available for apoE-related disorders, several promising candidates deserve further improvement and exploitation.

APOE genotype and stress response - a mini review

The APOE gene is one of currently only two genes that have consistently been associated with longevity. Apolipoprotein E (APOE) is a plasma protein which plays an important role in lipid and lipoprotein metabolism. In humans, there are three major APOE isoforms, designated APOE2, APOE3, and APOE4. Of these three isoforms, APOE3 is most common while APOE4 was shown to be associated with age-related diseases, including cardiovascular and Alzheimer’s disease, and therefore an increased mortality risk with advanced age. Evidence accumulates, showing that oxidative stress and, correspondingly, mitochondrial function is affected in an APOE isoform-dependent manner. Accordingly, several stress response pathways implicated in the aging process, including the endoplasmic reticulum stress response and immune function, appear to be influenced by the APOE genotype. The investigation and development of treatment strategies targeting APOE4 have not resolved any therapeutic yet that could be entirely recommended. This mini-review provides an overview on the state of research concerning the impact of the APOE genotype on stress response-related processes, emphasizing the strong interconnection between mitochondrial function, endoplasmic reticulum stress and the immune response. Furthermore, this review addresses potential treatment strategies and associated pitfalls as well as lifestyle interventions that could benefit people with an at risk APOE4 genotype.

Influence of the APOE genotype on hepatic stress response: Studies in APOE targeted replacement mice and human liver cells

Apolipoprotein E (APOE) is a multifunctional plasma protein mainly acting in lipid metabolism. Human APOE is polymorphic with three major isoforms (APOE2, APOE3 and APOE4). Up to 75% of the body's APOE is produced by the liver. There is increasing evidence from studies in brain-derived cells that APOE4 affects mitochondrial function and biogenesis as well as stress and inflammatory responses - processes, whose disturbances are considered hallmarks of the ageing process. However, although the liver is the main production site of APOE, knowledge about the impact of the APOE genotype on hepatic stress response-related processes is rather limited. Therefore, we studied biomarkers of oxidative status (glutathione levels, 3-nitrotyrosine adducts, protein carbonyl concentration), ER stress (XBP1(S), BiP, DDIT3), proteasome activity, mitochondrial function (respiratory complexes, ATP levels and mitochondrial membrane potential as well as biomarkers of mitochondrial biogenesis, fission and fusion), autophagy (LC3, LAMP2A), apoptosis (BCL2, BAX, CYCS) and DNA damage in the liver of APOE targeted replacement (TR) mice and in Huh7 hepatocytes overexpressing the APOE3 and the APOE4 isoform, respectively. APOE4 mice exhibited a lower chymotrypsin-like and a higher trypsin-like proteasome activity. Levels of protein carbonyls were moderately higher in liver tissue of APOE4 vs. APOE3 mice. Other biomarkers of oxidative stress were similar between the two genotypes. Under basal conditions, the stress-response pathways investigated appeared largely unaffected by the APOE genotype. However, upon stress induction, APOE4 expressing cells showed lower levels of adenosine triphosphate (ATP) and lower mRNA levels of the ATP-generating complex V of the mitochondrial respiratory chain. Overall, our findings provide evidence for a rather low influence of the APOE genotype on the hepatic stress response processes investigated in this study.

Variability in APOE genotype status in human-derived cell lines: a cause for concern in cell culture studies?

Although cell culture studies have provided landmark discoveries in the basic and applied life sciences, it is often under-appreciated that cells grown in culture are prone to generating artifacts. Here, we introduce the genotype status (exemplified by apolipoprotein E) of human-derived cells as a further important parameter that requires attention in cell culture experiments. Epidemiological and clinical studies indicate that variations from the main apolipoprotein E3/E3 genotype might alter the risk of developing chronic diseases, especially neurodegeneration, cardiovascular disease, and cancer. Whereas the apolipoprotein E allele distribution in human populations is well characterized, the apolipoprotein E genotype of human-derived cell lines is only rarely considered in interpreting cell culture data. However, we find that primary and immortalized human cell lines show substantial variation in their apolipoprotein E genotype status. We argue that the apolipoprotein E genotype status and corresponding gene expression level of human-derived cell lines should be considered to better avoid (or at least account for) inconsistencies in cell culture studies when different cell lines of the same tissue or organ are used and before extrapolating cell culture data to human physiology in health and disease.

Myeloid deletion of nuclear factor erythroid 2-related factor 2 increases atherosclerosis and liver injury

OBJECTIVE

To determine the impact of hematopoietic deletion of nuclear factor- (erythroid-derived 2) like 2 factor (Nrf2) on the development of atherosclerosis and liver injury in an obese, hypercholesterolemic mouse model.

METHODS AND RESULTS

Two-month-old male low-density lipoprotein receptor-deficient mice were lethally irradiated and transplanted with either wild type or Nrf2-deficient (Nrf2(-/-)) bone marrow cells. At 3 months of age, mice were placed on an obesogenic high-fat diet (HFD), high-cholesterol diet for 7 months. Despite no differences in body weight, body fat percentage, liver fat, plasma glucose, lipids, or insulin, the HFD-fed Nrf2(-/-) bone marrow recipients had increased proinflammatory vascular gene expression, a significant increase in atherosclerosis area (18% versus 28%; P=0.018) and lesion complexity, and a marked increase in liver fibrosis. The acceleration of vascular and liver injury may arise from enhanced macrophage migration, inflammation, and oxidative stress resulting from myeloid Nrf2 deficiency.

CONCLUSIONS

Myeloid-derived Nrf2 activity attenuates atherosclerosis development and liver inflammation and fibrosis associated with obesity. Prevention of oxidative stress in macrophage and other myeloid lineage cells may be an important therapeutic target to reduce inflammation-driven complications of obesity.

Dietary polyphenols as modulators of brain functions: biological actions and molecular mechanisms underpinning their beneficial effects

Accumulating evidence suggests that diet and lifestyle can play an important role in delaying the onset or halting the progression of age-related health disorders and to improve cognitive function. In particular, polyphenols have been reported to exert their neuroprotective actions through the potential to protect neurons against injury induced by neurotoxins, an ability to suppress neuroinflammation, and the potential to promote memory, learning, and cognitive function. Despite significant advances in our understanding of the biology of polyphenols, they are still mistakenly regarded as simply acting as antioxidants. However, recent evidence suggests that their beneficial effects involve decreases in oxidative/inflammatory stress signaling, increases in protective signaling and neurohormetic effects leading to the expression of genes that encode antioxidant enzymes, phase-2 enzymes, neurotrophic factors, and cytoprotective proteins. Specific examples of such pathways include the sirtuin-FoxO pathway, the NF-κB pathway, and the Nrf-2/ARE pathway. Together, these processes act to maintain brain homeostasis and play important roles in neuronal stress adaptation and thus polyphenols have the potential to prevent the progression of neurodegenerative pathologies.

ApoE genotype: from geographic distribution to function and responsiveness to dietary factors

ApoE is a key protein in lipid metabolism with three major isoforms.ApoEallele frequencies show non-random global distribution especially in Europe with highapoEε3frequency in the Mediterranean area, whereas theapoEε4genotype is enriched in Northern Europe. TheapoEε4genotype is one of the most important genetic risk factors for age-dependent chronic diseases, including CVD and Alzheimer's disease (AD). The apoE polymorphism has been shown to impact on blood lipids, biomarkers of oxidative stress and chronic inflammation, which all may contribute to the isoform-dependent disease risk. Studies in mice and human subjects indicate that theapoEε3but not theapoEε4genotype may significantly benefit from dietary flavonoids (e.g. quercetin) andn-3 fatty acids. Metabolism of lipid soluble vitamins E and D is likewise differentially affected by theapoEgenotype. Epidemiological and experimental evidence suggest a better vitamin D status inapoEε4than ε3subjects indicating a certain advantage of ε4over ε3. The present review aims at evaluation of current data available on interactions between apoE polymorphism and dietary responsiveness to flavonoids, fat soluble vitamins andn-3 fatty acids. Likewise, distinct geographic distribution and chronic disease risk of the different apoE isoforms are addressed.

Apolipoprotein E genotype affects tissue metallothionein levels: studies in targeted gene replacement mice

The apolipoprotein E (APOE) genotype is an important risk factor for ageing and age-related diseases. The APOE4 genotype (in contrast to APOE3) has been shown to be associated with oxidative stress and chronic inflammation. Metallothioneins (MT) exhibit antioxidant and anti-inflammatory activity, and MT overexpression has been shown to increase lifespan in mice. Interactions between APOE and MT, however, are largely unknown. Hence, we determined the effect of the APOE4 versus APOE3 genotype on MT levels in targeted gene replacement mice. APOE4 versus APOE3 mice exhibited significantly lower hepatic MT1 and MT2 mRNA as well as lower MT protein levels. The decrease in hepatic MT protein levels in APOE4 as compared to APOE3 mice was accompanied by lower nuclear Nrf1, a protein partly controlling MT gene expression. Cell culture experiments using hepatocytes identified allyl-isothiocyanate (AITC) as a potent MT inductor in vitro. Therefore, we supplemented APOE3 and APOE4 mice with AITC. However, AITC (15 mg/kg b.w.) could only partly correct for decreased MT1 and MT2 gene expression in APOE4 mice in vivo. Furthermore, cholesterol significantly decreased both Nrf1 and MT mRNA levels in Huh7 cells indicating that differences in MT gene expression between the two genotypes could be related to differences in hepatic cholesterol concentrations. Overall, present data suggest that the APOE genotype is an important determinant of tissue MT levels in mice and that MT gene expression may be impaired by the APOE4 genotype.